81619993 has 16 divisors (see below), whose sum is σ = 103699456. Its totient is φ = 62493120.

The previous prime is 81619987. The next prime is 81620027. The reversal of 81619993 is 39991618.

It is a cyclic number.

It is not a de Polignac number, because 81619993 - 2⁵ = 81619961 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81619393) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11646 + ... + 17287.

It is an arithmetic number, because the mean of its divisors is an integer number (6481216).

Almost surely, 2^81619993 is an apocalyptic number.

It is an amenable number.

81619993 is a deficient number, since it is larger than the sum of its proper divisors (22079463).

81619993 is a wasteful number, since it uses less digits than its factorization.

81619993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28984.

The product of its digits is 104976, while the sum is 46.

The square root of 81619993 is about 9034.3783958831. The cubic root of 81619993 is about 433.7759980763.

The spelling of 81619993 in words is "eighty-one million, six hundred nineteen thousand, nine hundred ninety-three".